Process for the polymerization of olefins



Plat d Sept- 26,19 2,174,247-

UNITED STATES PATENT OFFICE Sumner B. llcllllister, Lafayette, Calif,assignor to Shell Development Company, San Francisc Call! a corporationof Delaware No Drawing- Application March as, 1937, Serial No. 133,203

1 Claims. (01. zap-cs3) This invention relates to the manufacture oftainable. It may be carried out in many diflerolefln polymers, and, morespecifically, is conout ways. cerned with a method wherein olefins arepoly- For the purpose of making my invention clear merized by contactwith strong mineral acids it will be describedwith more particularreference 5 without resort to -a separate step of olefin abto themanufacture of octenes from butane- 5 sorption. butylene fractionsobtainable from the products An important object of my invention is theproof petroleum: cracking, using aqueous sulfuric vision of a processwhereby the yield of polymers acid as the polymerizing agent. It will beunderof desired characteristics from a given oleflnic stood, however,that this is merely for purposes of mixture canbe materially increased.'Ihe'process illustration and implies no limitation on my in- 10 hasspecial advantages in the manufacture of veiltion as the same, orequivalent, procedures anti-knock motor fuels, for example, since by itsmay be used for the polymerization of other mixuse a gasoline can beproduced having ahigher tures containing tertiary and secondary olefinsoctane rating than is obtainable by polymerlzaregardless of the sourceor other constituents of tion of the same amounts of the same starting;the mixture. Thus, tertiary olefins which may be 15 olefins by priormethods. present in the mixtures which may be used in the Inorder thatthe scope of my inventionbefuliy process of my invention include, inaddition to comprehended, the following terminology is deisobutylene,trimethylethylene, unsymmetrical fined: p methyl ethyl ethylene,tetramethylethylene and Tertiary olefins are those olefins which containthe like while typical secondary olefins which may 20 an unsaturatedtertiary carbon atom be present therewith are, for example, propylene,

a and p butylene, o: and p amylene, 2-methyl pen-- 7 4 l I tone-4, etc.The olefins may be used in a pure c=c state as mixtures of one or moretertiary-olefin with one or more secondary olefins or suchmixturescontaining other components such, for exinitially or those, likeisopropyl ethylene, which mple, as paraflins and/ r iol flns. may beisomerize in'the presence of strong mineral acids useda t c la y smta lare hydrflcal'bbll to such a form. Secondary olefins are normal or rations consisting of. r pr n nsin. hy-

3 iso-oleflns, other than ethylene, containing the drocarbons containingthe same number of carbon roup CH=CH--. The intermolecular combinaatomsto the molecule altho nonisomeric mixtures 'tion of like olefinmolecules is termed copolyme'ricontaining tertiary and secondary olefinszation while the combination of unlike olefin also be used. Furthermoreinstead of sulfuric for exampleyth reaction of a tertiary with acid,other suitable strong mineral acids, such secondary olefin or of acopolymer of either with s ph sphoric, benzene u n and like acids,

a different olefln will be "referred to as oonjunet for example, ortheir mixtures may be employed polymerization. as polymerizing agent.

I have iound-that tertiary olefins may be ne- One simple method ofcarrying out the conacted with secondary olefins and/or other teriunctpolymerizat on pr s of my i v t 40 tiary olefins to give high yields ofconjunct polycomprises contacting a preheated butane-butylmers byheating mixtures of sucholefins with one fraction containing isobutyleneand o: and p aqueous mineral acids. While some copolymeributylenes, forexample, with to sulfuric zation may accompany this reaction in theprocacid, in a mixing pump which feeds to a separator 4 es ofmyinvention, it leads to a commercially in which the reaction mixture isstratified, the 5 practical method for materially increasing the acidlayer being returned to the pumpwhile the yield of olefin polymers frommixtures containing hydrocarbon layer is fractionated for separationboth tertiary and secondary olefins. .Hy process of polymers fromunreacted hydrocarbons, etc. is simple,- may be carried out in readilyavailable The process is preferably carried out under sufequipment andis easily controlled, particularly flcient pressure-to maintain thebutylenes subwithrespecttothedegreeof polymerimtionobstantiallyin theliquid state for which P e about 300 pounds pressure is ample, when thereaction is carried out in the preferred range of about 80 C. to about120 C. Typical of the results obtainable by this procedure are thefollow-- n Example I Composition of feed, weight per cent:

Isobutylene 18. 5 i u. and p butylenes 28. 2 Butanes 53. 3

Sulfuric acid concentrationper cent 69. 6

Molal ratio acid to olefin in mixer 0. 51

Pressure, lbs/sq. in. gauge 290-310 Temperature of mixer C 100 Averagecontact timeminutes 10 Composition of product,- weight 'per cent:

Isobutylene 0. 1 a and p butylenes" 15. 5 Butanes 53. 3 Polymers L 31. 1

I Per cent isobutylene reacted 99. 5

Per cent a and p butylenes reacted 45. 1

Weight per cent octenes in polymer 86. 8

Octane rating of hydrogenated dimer 99. 6

Example II a Composition of feed, weight percent:

Isobutylene 18. 5 a and s butylenes 28. Butanes 53. Sulfuric acidconcentration per cent 70. 0 Moi ratio acid to olefin in mixer 0. 43Pressure. lbs./sq. in. gauge 300 Temperature of mixer c. 100 Averagecontact time minutes 10 Composition of product, weight per cent:

Isobutylene 0.0 a and p butylenes 9.5 Butanes 53. 5 Polymer 37. 0 Percent reacted, based onfeed:

Isobutylene per cent..- 100 a. and p butylenes do 64. 8 Weight per centof octenes in polymer 88.6 Octane rating of hydrogenated dimer 99. 1

By recycling the unreacted secondary olefins after removal of thepolymer, higher conversions may be obtained, as a high ratio. ofsecondary oleflns to tertiary olefins is conducive to more extensiveconjunct polymerization. Using the same mixer as in the foregoingexample, but recycling a volume of exit hydrocarbon equal to that of thefeed the following results were obtained.

The use of a mixer pump as described in Examples I and II isparticularly advantageous in that the ratio of tertiary 'olefins tosecondary olefins in the mixer tends to be lower than that in the feeddue to constant dilution of the mixture with fresh feed thus promotingconjunct polymerization. It also has the advantage of promoting intimatemixing of acid and olefins which is desirable for rapid and easilycontrolled polymerization. The conjunct polymerization of my inventionmay, however, be carried out in other types of apparatus. For example,the mixer may be replaced by a packed tower or other suitable contactingmeans. when using a tower type of reactor, a jet mixer, for example ofthe Venturi type. may be attached at'the top to intimately mix thereturned acid and hydrocarbon feed which may as before be either freshhydrocarbon alone or such hydrocarbon mixed with recycled unreactedsecondary olefins. By filling the tower while providing additionalreaction time.

with glass or porcelain chips or other inert packing, the degree ofmixing may be increased and as preferably the flow is downward, there isno accumulation of acid in the system. The tower may advantageously besuitably heated in order to maintain the desired reaction temperature.This method of operation has the advantage of eliminating corrosion ofthe moving parts of mixers, etc., and reduces the cost of the equipment.The capacity of a given reactor, whether of the tower or mixer or othersuitable type, may be increased by providing suitable waiting tanks inwhich stratification is substantially avoided In order to promoteintimate contact between acid and oleflnic mixture, mixers provided withwaiting tanks may be operated in series, it usually being unnecessary insuch cases to apply heat in the second polymerization stage. Anadvantageous alternative procedure to that described in Example 11 forthe recycling of unreacted olefins comprises returning to the mixeralong with fresh hydrocarbon and separated acid, a part of theemulsified reaction product before Stratification. In the case of seriesoperation of two or more mixers the recirculation of emulsion ispreferably from the last to the first stage.

Whatever method of operation is adopted, I find it preferable incarryingout the conjunct polymerization of isobutylene with secondarybutylenes for the production of octenes to use sulfuric acid of about 55to concentration and more preferably of 63 to 72% concentration, attemperatures of about 120 to about 70 C. and more preferably of about105 to C. The upper limit of both acid concentration and temperature isset by $0: formation which not only increases corrosion difficulties butalso introduces impurities into the polymer which are dimcult to remove,interfere with its hydrogenation and are otherwise objectionable. Byusing mixtures of phosphoric acid and/or phospha'tes, such, for example,as sodium acid phosphate, and the like, in suitable proportions such forexample, as about 5 to 25%, with the sulfuric acid, the formation of SO:may be effectively inhibited, however. In all cases I prefer to avoidexcessive temperatures as these necessitate the use of very highpressures to'maintain the olefins in the liquid state and this undulyincreases the cost of the equipment. Sulfuric acid of below 63% is morecorrosive than sulfuric acid of higher effective concentrations, butvery concentrated acid of 80% or above tends to increase the higherpolymer content of the product at the expense of octene production. Itherefore prefer to operate in the specified preferred ranges using thehigher temperatures with acid of lower concentrations and vice versa.

Other things being equal, the longer the contact time the greater theamount of reaction. with stronger acids and higher temperatures theinfluence of time is less. marked than under milder conditions, however.Thus in operations at about very little difference in the amount ofisobutylene and secondary butylenes reacted or in the amount of octenesin the product at'reaction times of about 3 to 10 minutes. With 65% acidon the other hand the amount of secondary oleflns reacted continues toincrease noticeably as the contact time at about 100 C. is increased toabout 13 minutes. A maximum reaction efficiency corresponds to maximumproduction of C. with 70% sulfuric acid there is conjunct polymers and Igenerally prefer not. to 1 amass? extend the reaction period much beyondthat necessary for the polymerization of equal amounts of tertiary andsecondary olefins.

The efiect of increasing the ratio of acid to olefins present is, up toa certain point which varies with the acid concentration andtemperature, to accelerate the reaction. Very low molar ratios ofsulfuric acid to butylenes, for example,

lower than about 0.25 to 1 are preferably not used with sulfuric acid of65% at 80 0., or similar mild conditions, as the conjunct polymerizationreaction is decreased thereby. Nor do I find any practical advantageusually in using a higher ratio than about 2.5 to 1. At highertemperatures and with stronger acid the influence of acid to olefinratio is less than that produced under milder conditions.-

It is'thus evident that my process is quite flexible and that by properadjustment of the factors of acid concentration, temperature, time ofcontact and ratio of acid to olefin within the following ranges, highyields of butene' dimers may be obtained in a simple manner.

Sulfuric acid concentration i per cent.. 55 to 80 or preferably 63 to 72Temperature C.. 120 to 70 or preferably 105 to 80 Time of contact'minutes 1 to 25 or preferably 3 to 13 Molar ratio H2304 to.butenes 2.5to 0.25 or preferably 1.5 to 0.5

Another factor which may be regulated to promote the formation of dimersby which I'mean polymers composed of two molecules of starting olefinwhether like olefins or, as in conjunct polymerization, unlike olefinsinstead of higher polymerization products, is the inert hydrocarboncontent. This may be varied by direct addition of hydrocarbon to thereaction mixture or by-recycling inert hydrocarbon recovered from thereaction products whether containing unreacted' oleflns or not. Suitablehydrocarbons which are inert under the conditions of the reaction arefor example, paraiifins, aromatics such as benzene, etc., saturatedcarbocyclic compounds, and the like. Most preferably inert hydrocarbonswhich are easily removed from the desired polymerization productbydistillation are used when resort is had to direct addition ofhydrocarbon. I prefer not to use hydrocarbons boiling at temperatureslower than that of the olefins being treated, however, as the pressurerequired to-maintain the system substantially in the liquid phase isincreased thereby. In some cases it is permissible to use hydrocarbonsof about the same boiling range as that of the product as for example,

where polymers are being manufactured for blending with gasoline toincrease its octane rating, the gasoline, in part or in whole, may beadd ed as the desired hydrocarbon. The effect of the inert hydrocarbon,whether initially present or added or both, appears to be that of asolvent for, or diluent of, the polymer formed so that there islesscontact of polymer with acid after the dimer stage is reached thanin the absence of such inert hydrocarbon and consequently the yields 01'dimer are increased thru suppression of I the reaction of dimer withmono-oleflns and/or other dimers to produce higher polymerizationproducts.

i For the production oi conjunct polymers by the process of my inventionit is advantageous to.

have a substantial amount of tertiary olefin present also preferably atleast as many mols 01 secondary olefin present asthere are mols oftertlary olefin and more preferably, as has already been pointed out, anexcess or secondary olefins over tertiary oleflns. for example, about1.5 to r about 5.0 mols of secondary butylenes per mol of isobutylene.When the amount of secondary oleflns present is very small the reactionis almost exclusively copolymerization of isobutylene while withexcessive ratios of secondary oleflns the conversion is very low evenwhen very long contact times and very drastic conditions are used, asshown by the following tests carried out in th samenpparatus usedinExample I.

Example In" Composition of feed, weight per cent:

Depending upon conditions, more'or less oopolymerization may accompanythe conjunct polymerization in the processor my invention, but 1preferably regulate the reaction, as described, so that substantialconjunct polymerization is efiected as in this manner not only arehigher yields of suitable products obtained but also higher conversionsper unit volume of reactor space are obtained. It is thus evident thatthe process of my invention oflers many advantages over .prior methodsof polymerizing olefins. It eliminates entirely the olefin absorptionstep formerly thought to'be essential in order to obtain high dimeryields, yet produces even higher proportions of dimers. It permits theconversion of both tertiaryand secondary olefins to valuablepolymerization products without resort to theme of solid catalysts whichare subject to poisoning and deterioration and which require hightemperatures with attendant control difliculties. In the manufacture ofanti-knock gasoline, the process of my invention yields more octanegallons (i. e. gallons of product multiplied by its octane number,before or after hydrogenation) than are obtainable by processing thesame olefins "by other known methods. This is believed to be due to thefact that it employs relatively less drastic conditions than priormethods. such for example, as 'vapdr phase polymerization with.

solid catalysts which encounter serious difilculty from undesirable sidereactions such as isomerization "to products of lower octane rating,etc., yet permits substantial secondary olefin reaction and'theretorehigher gallonagethan prior methods using aqueous acid catalysts. Thelife ot the catalyst in my process is exceptionally long, more thanvolumes of hydrocarbon having beentreated per volume of sulfuric acid'without materially aiiectlng the activity or theacid; -,Many

variations maybe introduced without' departing from the spirit ofmy'inv'ention which is. not as" be regarded-as limited to the detailsot'qperation disclosed nor by the soundness of thetheories advanced inexplanation or the improved results attained, but only by the terms ofthe accompanying claims in which it is my intention to claim all noveltyinherent therein as broadly as possible in view of the prior art.

I claim as my invention:

1. A process for producing olefin polymers which comprises maintaining ahydrocarbon mixture containing different olefins of at least threecarbon atoms at least one of which'is a tertiary olefin in contact withan aqueous solution of a strong mineral acid of sulfur of 55to 80%concentration at a polymerizing temperature of about 120 to about C.until substantial conjunct polymerization between said olefins takesplace.

2. A process for producing polymers from a hydrocarbon mixturecontaining tertiary and secondary olefins which comprises heating saidhydrocarbons in the liquid phase with a 55 to sulfuric acid solution atabout 120 to 70 C. until substantial conjunct polymerization of tertiaryolefin with secondary olefin takes place.

3. A process for producing polymers from a hydrocarbon mixturecontaining tertiary and secondary olefins which comprises contactingsaid hydrocarbons in the liquid phase with about 0.25 to about 2.5 molsof sulfuric acid per mol of olefin at about 70 to 120 C., the acidconcentration being 80% to 55%, until substantial conjunctpolymerization of tertiary olefin with secondary olefin takes place.

4. A process for producing octenes from isobutylene and secondarybutylenes which comprises contacting said olefins with about 0.25 toabout 2.5 mols of sulfuric acid at about 70 to 120 C., for a timebetween 1 minute and about 25 minutes, using an acid concentrationwithin the range of about 55% to 80% which promotes substantial conjunctpolymerization of isobutylene with secondary butylene under the reactionconditions.

5. In a process for producing anti-knock gasoline from tertiary andsecondary olefins of not more than six carbon atoms per molecule thesteps of contacting a mixture comprising said olefins and 55 to 80%sulfuric acid at a temperature of about 120 to 70 C. and maintainingsaid components in emulsified contact until substantial conjunctpolymerization of tertiary olefin with secondary olefin takes place.

6. A process for producing olefin polymers which comprises contacting atertiary olefin containing mixture containing at least one and not morethan five mols of secondary olefin per mol of tertiary olefin with 55 to80% sulfuric acid at 120 to 70 C. until substantial conjunctpolymerization of tertiary olefin with secondary olefin takes place.

'1. A process for producing olefin polymers which comprises contacting amixture of tertiary and secondary olefins with 55 to 80% sulfuric acidat 120 to 70 C. in the presence of an effective amount of asubstantially inert hydrocarbon until substantial conjunctpolymerization of tertiary olefin with secondary olefin takes place.

8. A process for producing olefin polymers which comprises heating ahydrocarbon mixture containing tertiary and secondary olefins,contacting the heated hydrocarbon with 55 to 80% sulfuric acid andmaintaining said hydrocarbon and acid in emulsified contact at about 120to 70 C. until substantial conjunct polymerization of tertiary olefinwith secondary olefin takes place.

9. A continuous process for polymerizing olefins which comprisescontinuously feeding heated hydrocarbon in the liquid phasecontaining'tertiary and second olefins to an emulsifier with 55 to 80%sulfuric acid, maintaining said hydrocarbon and acid in emulsifiedcontact at about 120 to 70 C. until substantial conjunct polymerizationof tertiary olefin with secondary olefin takes place, separatingpolymers and acid from the reacted mixture and continuously returningthe latter together with at least a part of the" unreacted olefinrecovered to the emulsifier for contact with further tertiary andsecondary olefin containing hydrocarbon.

10. A process for producing octenes which comprises emulsifying abutane-butylene fraction containing isobutylene and an excess ofsecondary butylenes with 63 to 72% sulfuric acid at to 80 C. for a timewithin the range of about 3 to 13 minutes suflicient for substantialconjunct polymerization of isobutylene with sec ondary butylenes,stratifying the reacted mixture, separating polymers produced andreturning at least a part of the unreacted butylenes to contact withsaid acid and fresh butane-butylene fraction.

11. A process for producing octenes which com prises feeding anemulsified mixture of 63 to 72% sulfuric acid and hydrocarbonscontaining isobutylene and secondary butylenes to a packed columnmaintained at a temperature of from 105 to 80 C. at a rate at whichsubstantial conjunct polymerization of isobutylene with secondarybutylene takes place therein, separating the resulting polymers andreturning the acid to the emulsifier.

SUMNER H. MCALLISTER.

Fry

